1. Field of the Invention
The present invention relates to a cleaning method in a process of producing semiconductor integrated circuits having a conductive metal film on a semiconductor wafer, wherein cleaning is carried out after the removal of a photoresist with a removing agent, and to a rinse for cleaning semiconductor devices that will be used in the above cleaning.
2. Description of the Related Arts
In the production of a semiconductor integrated circuit, a conductive film for a metal wiring material is formed on a semiconductor wafer by such a technique as sputtering and CVD. Then, a photoresist is applied to the conductive film and is exposed and developed by photolithography to form a pattern and the unmasked portion of the conductive film is dry-etched with a reactive gas, allowing the photoresist to serve as a mask thereby forming a fine wiring.
Thereafter, a method of removing the above photoresist film from the conductive film or a method wherein, after the formation of the fine wiring, ashing is carried out to remove the resist residue remaining on the masked portion from the conductive film is taken.
Conventionally, as photoresist removers used in these methods, acid removers and basic removers are generally used.
However, since the acid removers are weak in removing power and are strong in corrosive action on conductive metal films used for fine wiring processing, they are not so often used in recent fine wiring processing wherein strict dimensional accuracy is required.
On the other hand, since the basic removers are high in resist removability, they are recently used widely in fine wiring processing. The following basic removers can be mentioned:
(1) an aqueous solution remover comprising a quaternary ammonium hydroxide as a main agent (e.g., Japanese Patent Application Laid-Open Nos. 2325/1989 and 48633/1992) PA1 (2) a remover comprising an alkanolamine as a main agent (e.g., Japanese Patent Application Laid-Open Nos. 88548/1989 and 222573/1994) PA1 (3) a remover comprising an alkanolamine as a main agent and a reducing agent as an auxiliary (e.g., Japanese Patent Application Laid-Open Nos. 289866/1992 and 266119/1994)
The aqueous solution remover (1) comprising a quaternary ammonium hydroxide as a main agent greatly corrodes the conductive metal film of aluminum, an aluminum alloy, titanium, tungsten or the like as a wiring material and the corrosive action thereof is further accelerated in the case wherein pure water or ultrapure water is used as a rinse, leading to the problem that a phenomenon of corrosion in the form of numerous pits or craters takes place on the metal surface.
In the case wherein a quaternary ammonium hydroxide is used as a main agent and a saccharide or a sugaralcohol is added thereto (Japanese Patent Application Laid-Open No. 48633/1992), although corrosion of a conductive metal film is inhibited, the occurrence of a phenomenon of corrosion in the form of pits or craters cannot be avoided when pure water or ultrapure water is used as a rinse.
In the case of the remover (2) comprising an alkanolamine as a main agent, generally an alcohol, such as methanol and propanol, is used as a rinse and in addition thereto rinsing is carried out using pure water or ultrapure water. If the cleaning with an alcohol is not carried out satisfactorily, corrosion of the conductive metal film takes place in the subsequent cleaning with pure water or ultrapure water, leading to a phenomenon of corrosion in the form of pits or craters.
Further, in the case wherein after a remover comprising an alkanolamine as a main agent is used, rinsing is carried out directly using pure water or ultrapure water as a rinse without using an alcohol as a rinse, a phenomenon of corrosion of the conductive metal film proceeds extremely and the occurrence of the phenomena of corrosion in the form of numerous pits or craters cannot be avoided.
In the above (3), an alkanolamine is used as a main agent and a reducing substance, such as a hydroxylamine, is used as an auxiliary. In this case as well, generally, cleaning with an organic solvent, such as an alcohol, as a rinse is carried out and then cleaning with pure water or ultrapure water as a rinse is carried out. In some cases, cleaning with pure water or ultrapure water as a rinse is directly carried out without using an organic solvent, such as an alcohol. In both the former case and the latter case, a phenomena of corrosion takes place in the same manner as in the case of the remover (2).
Incidentally, Japanese Patent Application Laid-Open No. 184595/1994 discloses that after a basic remover is used, cleaning with a hydroxycarboxylate solvent, an alkoxycarboxylic acid solvent, an amide solvent, a lactone solvent, a sulfur compound solvent, or the like as a rinse instead of an alcohol is carried out and then cleaning with pure water or ultrapure water as a rinse is carried out. In this case as well, the same problem as that in the cases of the removers (2) and (3) is brought about, and with respect to a phenomenon of corrosion of aluminum or the like, no improvements have been achieved.
In a recent ultrafine processing technique involved in a wiring step wherein strict dimensional accuracy is required, a flammable hazardous material, such as an alcohol, has to be used as a rinse in a large amount if a basic remover is used, and any countermeasures cannot be found against corrosion in the form of craters or pits which is caused when pure water or ultrapure water is used. Therefore, it is desired to develop a safe cleaning method wherein a phenomenon of corrosion of conductive metal films is not noted.
On the other hand, in dry-etching the above conductive film, a protective deposited film that is a reaction product of a reactive gas with the resist is formed. If this protective deposited film is left, it causes breakage of wires or abnormal wiring, leading to various troubles. Therefore, it is desired to remove the protective deposited film completely. Although acid or basic organic removing agents are conventionally used generally, these removing agents are not suitable for recent ultrafine wiring processing wherein dimensional accuracy is strict because these removing agents are accompanied by such defects that they are used at high remove temperatures or are highly dangerous because of their flash points and corrode the conductive film of a metal used in ultrafine wiring processing.
Further, in the case of the above removing agents, after the removal, since a large amount of an organic solvent, such as an alcohol, is used as a rinse, it is dangerous and the step is complicated as well. In recent years, use is made, for example, of a removing agent wherein a fluorine compound is dissolved in an organic solvent, such as ethylene glycol, or a removing agent in the form of an aqueous solution comprising an organic anticorrosive agent added to a fluorine compound (Japanese Patent Application Laid-Open No. 201794/1995) as a safe and simple remove means. These fluorine-based removing agents have such advantages that the removal temperature may be ordinary temperatures and ultrapure water or pure water can be used as a rinse.
However, even if these fluorine-based removing agents are used, corrosion in the form of fine pits or craters occurring on the metal surface cannot be avoided. With respect to the basic organic removing agents, acid organic removing agents, or fluorine-based removing agents, countermeasures against such corrosion have not been found and therefore there is desired a safe and simple removing method that does not cause a phenomena of corrosion of metal wiring materials taking rinses into account.
Therefore, an object of the present invention is to provide a method of producing a semiconductor device wherein a photoresist film applied to a conductive metal film formed on a semiconductor wafer, a photoresist layer remaining after etching, any resist residue (protective deposited film or side wall protective film) remaining after etching followed by ashing, or the like is removed with a remover, which method can produce a highly accurate circuital wiring by carrying out the removal and cleaning in a safe and simple manner without corroding the conductive metal film at all.